The present disclosure relates to a neutron imaging detector and a method for detecting neutrons. More particularly, the present disclosure relates to a neutron imaging detector including one or more neutron imaging integrated circuit (NIICs) and a method for detecting neutrons using one or more NIICs.
To advance nuclear power as a resource capable of meeting the future energy needs through novel and safer reactor designs and fuel types, it is necessary to develop new and advanced fuels with enhanced predictability of fuel behavior under a broad range of abnormal conditions, including loss-of-coolant related accident scenarios that may cause fuel damage and melting. These novel fuels may be considerably different from existing fuels or those tested in the past, with changes including different shapes to enhance their cooling performance, different compositions to help significantly reduce the amount of waste generated during the production of nuclear energy, and different materials to improve their thermal and safety performance.
Developing and proving the basis for safe operations of advanced reactors and nuclear fuels require a thorough understanding of what could happen to nuclear fuel if it were subjected to accident conditions, such as large power increases and loss-of-cooling events. Transient tests allow such assessments and are crucial in demonstrating the safety basis of the reactor and the fuel, thus establishing what constitutes safe reactor operating levels. To meet these needs, a comprehensive transient testing program has to be established.
Transient testing involves placing fuel, either previously irradiated or un-irradiated, contained in a test assembly into the core of a nuclear test reactor and subjecting it to short bursts of intense, high-power radiation. During testing, the test assembly is monitored using specialized instruments, such as a hodoscope. Before and after the transient experiment is conducted, however, the fuel or material is nondestructively examined (NDE) to determine the effects of the radiation on the physical and chemical configuration of the nuclear fuel. Neutron radiography of the used nuclear fuel can be performed at the Hot Fuel Examination Facility (HFEF) using, for example, the Neutron Radiography Reactor (NRAD) at the Idaho National Laboratory (INL).
While current state-of-the-art X-ray radiography hardware/software packages allow NDE of various objects, X-ray techniques are of limited use in imaging the spent fuel. This is because the overwhelming gamma background from the fuel, which is as high as 103-106 R/hour, obscures X-ray data. Thermal neutron radiography has proven to be the method of choice for this application.
Neutron radiography, using the foil-film transfer method, is currently employed for the quantitative evaluation of the geometric and compositional characteristics of fuel burnup distribution, visualization of cracks and void formations, fuel location determination, pellet-clad and pellet-pellet gaps identification, and to understand the state of non-fuel component geometries. Although the foil-film transfer method is gamma insensitive and provides large area high spatial resolution radiographs, this process takes approximately 24 hours to produce an image, which is impractical for neutron tomography. Tomographic reconstruction is of significant importance for the desired application as it allows real-time 3D visualization of the state of the fuel, which is important for imaging multidirectional cracks within the fuel pellets and density and/or burnup variations through the fuel rods.
Thus, there is a need for developing a high resolution digital neutron radiography detector that can simultaneously provide high spatial resolution of 10 lp/mm or better, fast data acquisition times on the order of minutes, high efficiency for thermal neutrons, minimal or no sensitivity to gamma background, that can operate in a high radiation environment and is capable of imaging highly radioactive specimens.